A Typical Spring Month: April 2009 Overview

Dr. David A. RobinsonNew Jersey State ClimatologistCenter for Environmental Prediction, School of Environmental and Biological
Sciences/NJAES, Rutgers UniversityMay 5, 2009

A typical April day in New Jersey is often perceived as one with sunshine, mild temperatures, and perhaps a stray shower added to the mix. In reality, April is a month of wild weather swings, often within several days, occasionally in several hours! April 2009 was quite typical in that department. Only a few snow flurries fell on the 8th, however temperatures fell below freezing as late as the 24th. Coastal areas were wet, while below-average precipitation fell in the northwest. Thunderstorms rumbled on five days, with hail reported on three of those days. Winds exceeded 40 mph on eleven days at one or more locations. The last week brought a four-day 90° heat wave to much of the state, one of the longer such April events on record.

Yet in spite of the wide swings in weather, the monthly statewide mean temperature of 52.5° was 2.0° above average. Without the heat wave, the month would have been close to normal (assuming those days had been close to average). Of course those four days cannot be discounted, thus April 2009 checks in as the 22nd warmest (tied with 1938, 1957, and 2005) of the past 115 years.

While there was quite a variation in April precipitation across NJ, the 4.53" statewide mean was just 0.60" above average or the 32nd wettest on record. The southeast was wettest, with 8.32" at Little Egg Harbor (Ocean County) and Stafford Township (Ocean) with 7.12", and Berkeley Township (6.95"; Ocean) topping the list of Community Collaborative Rain, Hail and Snow Network reports. On the low end, Andover Township (Sussex) received 2.18", Blairstown (Warren) 2.44" and Holland Township (Hunterdon) 2.56".

Despite the above-average statewide total for April, the January through April period brought an average of only 10.44" to NJ, ranking this as the 7th driest such start of the year on record. This is 4.56" below the mean or 70% of average. Thus the month ended with streams flowing well below average across NJ. The good news was that the water table was rising in the wetter south; such was not the case in the north.

Six April events brought at least an inch of rain to more than one location in the state. Thunderstorms on the 3rd brought 1.41" to Randolph (Morris), with precipitation totals decreasing away from this county to only 0.25" in some locations. Showers and storms on the 6th brought 1.26" to Freehold (Monmouth) and 0.50"-1.00" to all but Delaware Valley locations in the southern half of NJ. The north saw 0.20"-0.50". Hail to the size of a nickel fell in Vineland (Cumberland). Thunder again rumbled in spots on the 10th, with scattered areas of 0.25"-0.50" in the south (a maximum of 1.10" at Belmar, Monmouth County) and little rain in the north. Ocean and Monmouth counties were the wettest on the 11th, with Berkeley Township (1.41") receiving the most. Anywhere from 0.25"-0.75" fell most everywhere else, except for less in the northwest, a frequent scenario during most of the month.

Coastal areas again were soaked on the 14th-15th, with 2.80" at Little Egg Harbor (Ocean). Other locations in this county topped 2.00", while the bulk of the south Jersey received 1-2". Meanwhile, about 0.50" fell in central counties and 0.25" in the north. Showers and thunderstorms crossed the state on the 20th. Harrison (Hudson) picked up 1.86" and Little Egg Harbor continued to see the monthly total grow, with 1.76" this time around. Most eastern areas from north to south picked up more than an inch. Some 0.75"-1.00" fell elsewhere, except again less in the northwest. Pea size hail fell in Hillsborough (Somerset) during the evening. The 21st brought more storms to the state, with 0.50" of rain in Hammonton (Atlantic) and pea size hail in Blairstown (Warren) and Jefferson Township (Morris).

Turning to the thermometer, the story the first three weeks or so of the month was cold morning temperatures. A number of locations dipped below freezing, with some well down into the 20s on several days. Most of these cold minima were a function of calm, clear nights, where temperature inversions result in colder temperatures at lower elevations. For instance, Walpack (Sussex) and Pequest (Warren) fell to 21° on the 9th. Pequest had the month's coldest reading of 19° on the 13th, with Walpack at 20°. The 16th saw Pequest at 24° and Walpack at 25°. Berkeley (Ocean) in the Pine Barrens was the coldest location on the 17th, dropping to 23°. Meanwhile, coastal Atlantic City Marina was as warm as 40°, high-elevation High Point was 38° and urban Newark was 37°.

The 24th brought what might be the last freezing morning of the season to portions of NJ. The "cold 3" came in at 25° (Walpack), 26° (Pequest) and 27° (Berkeley). The last freezing morning across the entire state was on March 24, when several coastal communities also fell below freezing.

With all the transitions from wet to dry and warm to cold, it was inevitable that windy conditions prevailed frequently during the month. This was reflected in the eleven days with 40 mph or greater gusts. On the 3rd, 4th, 5th, 12th and 15th, peak gusts were either 52 or 53 mph. High Point Monument (Sussex) took top honors on three of those days, Wantage (Sussex) on one and Atlantic City Marina on one. Peak gusts were between 40 and 49 mph on the 11th, 20th, 22nd, 23rd, 28th and 29th. The aforementioned stations led the way on four of those days, while Kingwood (Hunterdon) and Harvey Cedars (Ocean) topped the list on the other two days.

Unusually warm air invaded NJ on the afternoon of the 25th, when temperatures in most areas reached the mid 80s to low 90s. Toms River (Ocean) and Sicklerville (Camden) led the way at 92°. This was a remarkable day for thermal variations around the state, as the morning began at 39° in Walpack (Sussex) where it later climbed to 90°. Along the coast, Harvey Cedars only reached 68° and that was not until late evening when the land breeze warmed Long Beach Island. At 2PM, the temperature was 54° in Harvey Cedars while it was 90° at the Atlantic City Airport in Pomona (Atlantic)!

The heat peaked on the 26th, when most of the state was in the low to mid 90s. Sicklerville hit 96°. Meanwhile, Seaside Heights and Harvey Cedars reached 79°. This occurred at both locations between 10 and 11 AM before the sea breeze took charge and lowered temperatures about 10 degrees. Toms River (Ocean) and Howell (Monmouth) reached 95° on the 27th. Northeast and east central areas were impacted a bit by a backdoor cool front, keeping temperatures in the low 80s. For instance, in the Raritan basin, the maximum was 80° in New Brunswick (Middlesex), while less than 10 miles to the west, Hillsborough (Somerset) topped out at 94°.

The heat wave ended on the 28th, when a few stations around the state reached 90°. The southwesterly winds ahead of a cold front resulted in a more equitable distribution of high temperatures, as the coolest maximum was 78° at the Atlantic City Marina. To appreciate the unusual length of this April episode, the three days on which New Brunswick reached 90° or higher (25th, 26th, 28th) marked only the third time in the past century with either three (2002) or four (1976) such days in the month.

It was the state's good fortune that despite the wild twists of weather during the month, severe impacts were limited:

Thunderstorms only bordered on severe levels

Flooding was limited to the quick, local variety

Frequently blustery conditions did not result in notable damage

Only scattered brush and forest fires occurred during dry intervals (such as in Atlantic County on the 18th)

Vegetation was not far enough along to be affected by the occasional freezes

And the heat wave was not accompanied by debilitating humidity and two of the days fell on weekends, thus neither health nor power supplies were greatly stressed